Sodium lamps are the most effective group of visible radiation sources. They are characterized by high light transmission and a slight decrease in light flux during continuous operation.
Often sodium lamps are used for economical lighting of external objects - streets and construction sites, highways and tunnels, architectural structures, railway stations and airports, and other objects requiring contrast visibility in any weather conditions. In addition, such lamps are widely used for lighting flower beds and greenhouses with plants.
Arc sodium tube lamp (DNaT) is a glass cylinder containing a special "burner" - a cylindrical tube with pure aluminum oxide. This tube is filled with sodium and mercury vapor. In addition, these lamps contain starting gas - xenon.
There are two types of them - high-pressure sodium lamps, which allow to obtain monochrome light-orange radiation, as well as low-pressure, which provide about 200 lm / W, but are characterized by a warm color range.
It should be noted that sodium lamps are connected in a special way - using a special ballast and pulse-inflammatory device, although some manufacturers produce such lamps with a launch antenna, which has the form of a wire that wraps around a “burner”.
If we talk about the advantages of sodium lamps, then the following characteristics should be noted:
• high light output;
• long period of operation (up to 32 thousand hours);
• slight change in luminous flux during operation;
• economical use;
• range of working temperatures, which is -60 - +40 ° .
Despite the advantages listed above, sodium lamps have certain disadvantages:
• can be applied only when high requirements regarding good color rendering are not imposed. In addition, with prolonged use, they change their color range;
• the effectiveness of these lamps depends on the ambient temperature - in cold weather they shine worse;
• are not ecological, as they contain sodium compounds with mercury;
• they are recommended to be used only with minor fluctuations in the supply voltage;
• during operation, sodium atoms leak, which requires the use of a single-crystal discharge tube;
• at least 7 minutes must elapse to fully start this type of lamp and establish stable light characteristics.
Given these features of sodium lamps, they are best used in cases where a powerful and economical light source is required, and the correct color rendering is not very important.
It is worth noting that the power of these lamps should be selected in accordance with their use. So, for artificial lighting of flower gardens, greenhouses or nurseries for plants, it is best to use lamps with 150 or 250 watts. Sodium lamps for plants with a power of more than 400 watts are not used, as they are able to burn leaves. With the correct use of this light source, you can improve the growth of plants and grow them intensively throughout the year.